locate-java-home

> Locates JAVA_HOME on any platform, and can differentiate between different versions.


Usage

npm install @viperproject/locate-java-home

``js
import LocateJavaHome from '@viperproject/locate-java-home'; // or var LocateJavaHome = require('@viperproject/locate-java-home').default;
LocateJavaHome(function(error, javaHomes) {
javaHomes.forEach(function(homeInfo) {
console.log("Found Java " + homeInfo.version + " at " + homeInfo.path);
if (homeInfo.isJDK) {
console.log("It's a JDK!");
}
});
});

// Limit to JDKs for Java 6 and above.
LocateJavaHome({
// Uses semver :) Note that Java 6 = Java 1.6, Java 8 = Java 1.8, etc.
version: ">=1.6",
mustBeJDK: true
}, function(error, javaHomes) {
// Done.
});
`

Motivation

I originally wrote this utility for DoppioJVM,
which requires access to the Java 8 JDK during build time.

I required the following:

The ability to check the version* of java in JAVA_HOME.
* Verify that JAVA_HOME is a JDK and not a JRE.
Detect a Java 8 JDK even if it is not the default version of Java installed*.
* Have the above work across Windows, Mac, and Linux.

Since this functionality is likely generally useful, I have decided to release this
as a standalone library! Enjoy! :)




API

The locate-java-home package is a single async function that takes an optional options argument:

`js
LocateJavaHome(options, function(error, javaHomes) {});
LocateJavaHome(function(error, javaHomes) {});
`

javaHomes is an array of objects that contain information about each JAVA_HOME we found:

`typescript
{
// Absolute path to JAVA_HOME
path: string;
// Version of Java in the JAVA_HOME.
version: string;
// Security number of this version of Java.
// Typically, you want a version with the largest security number.
// Note: For Java 9 and later, this will always be '0' as this is now
// encoded into the version number. See http://openjdk.java.net/jeps/223
// and https://blogs.oracle.com/java-platform-group/a-new-jdk-9-version-string-scheme
security: number;
// True if this JAVA_HOME is a JDK, false if it is a JRE.
isJDK: boolean;
// Is this version of Java 64-bit?
is64Bit: boolean;
// Paths to various executables.
executables: {
java: string;
// JDK only:
javac: string;
javap: string;
}
}
`

Options

locate-java-home surfaces a number of useful options:

`typescript
{
// Semantic versioning string (e.g. ~1.6, >1.6....)
version: string;
// Are you specifically looking for a JDK over a JRE?
mustBeJDK: boolean;
// Are you specifically looking for a JRE over a JDK?
mustBeJRE: boolean;
// Are you specifically looking for a 64-bit JAVA_HOME?
mustBe64Bit: boolean;
// Do you want locate-java-home to exit fatally if one of the found JAVA_HOME
// locations does not function appropriately? (Mainly useful for debugging.)
paranoid: boolean;
}
`

Global Script

If you install locate-java-home globally, you'll have access to the locate-java-home command
line tool. Currently, it lists all of the JAVA_HOME` locations on your system. If there's any
desire to expand it into a full-fledged command line tool that exposes the options of this
library, let me know!